March 8, 2004
Dolores Beasley
Headquarters, Washington
(Phone: 202/358-1753)
William Jeffs
Johnson Space Center, Houston
(Phone: 281/483-5111)
RELEASE: 04-084
SPACE STATION RESEARCH YIELDS NEW INFORMATION ABOUT BONE LOSS
A new NASA-funded study revealed how bone loss increases the risk of
injuries, highlighting the need for additional measures to ensure the
health of spacecraft crews. The study provides new information about
bone loss caused by prolonged spaceflight. The study is in the online
version of the Journal of Bone and Mineral Research.
The research team was from the University of California San Francisco
(UCSF) and Baylor College of Medicine, Houston. The team used
three-dimensional X-ray computed tomography (CT) to study the effect
of prolonged weightlessness on the bone mineral density and structure
of the hip in a group of 14 American and Russian International Space
Station crewmembers. The crewmembers spent from four to six months
onboard the Station. The research suggests additional conditioning
exercises and other countermeasures may be necessary to prevent bone
mineral loss.
"This study underlines the importance of continuing to develop
countermeasures to preserve musculoskeletal conditioning in
long-duration space travelers," said Guy Fogleman, director of
Bioastronautics Research in NASA's Office of Biological and Physical
Research, Washington. "Results of this research, which may aid people
on Earth who suffer for similar conditions including osteoporosis,
are being shared with the medical community," he added.
This study is the first to use CT imaging to three-dimensionally
quantify spaceflight-related bone loss in the hip and to estimate
changes in hipbone strength. Previous studies used a two-dimensional
imaging technology called dual X-ray absorptiometry.
The CT measurements in the hip were performed pre- and post-flight to
measure bone loss in the porous bone in the interior of the hip and
in the dense outer shell of the hipbone. On average, the Station crew
lost interior bone at a rate of 2.2 to 2.7 percent for each month in
space and outer bone at a rate of 1.6 to 1.7 percent per month.
"Our study demonstrates that bone loss occurs in the Space Station
crewmembers at a rate comparable to that observed almost a decade
before in the crew of the Russian Mir spacecraft," said Thomas Lang,
UCSF associate professor of radiology and principal investigator on
the study. "The lack of clear progress in the interval between Mir
and Station missions indicates a need for continued efforts to
improve musculoskeletal conditioning regimens during longer space
missions, such as those proposed for the moon and Mars," Lang said.
The investigators used information from the CT images to estimate
changes in the strength of the hipbone. They found on average the
hipbone strength declined by 2.5 percent for each month of flight.
Since the amount of bone loss increases with mission length,
crewmembers on multiyear explorations may face increased risk of
fracture upon return to Earth gravity. In addition, those who do not
recover the lost bone may be at increased risk of fracture as they
age.
The researchers also analyzed loss of density in vertebrae (back
bones). Vertebrae, along with the hip, are the skeletal sites
associated most with serious osteoporotic fractures in the elderly.
The study found on average, the Station crew lost vertebral bone at a
rate of 0.8 to 0.9 percent per month, which was consistent with data
from earlier long-duration missions.
To view the study on the Internet, visit:
http://www.jbmr-online.org
For information about space research on the Internet, visit:
http://spaceresearch.nasa.gov/
For information about NASA on the Internet, visit:
http://www.nasa.gov/formedia
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